Photosynthesis and Cellular respiration study guide

Study Guide: Photosynthesis

Overview of Photosynthesis

Photosynthesis is the process by which autotrophic organisms (e.g., plants, algae, and some bacteria) convert light energy into chemical energy stored in glucose. It occurs in the chloroplasts and involves two main stages:

  1. Light-Dependent Reactions (convert light energy into ATP and NADPH)
  2. Calvin Cycle (Light-Independent Reactions, use ATP and NADPH to fix carbon into glucose)

1. Light-Dependent Reactions

  • Location: Thylakoid membrane (inside chloroplasts)
  • Purpose: Capture light energy to produce ATP and NADPH
  • Reactants: Light, H₂O, ADP + Pi, NADP⁺
  • Products: O₂, ATP, NADPH

Key Steps:

  1. Light Absorption
    • Light is absorbed by chlorophyll
  2. Water Splitting
    • Light splits water molecules into O₂, H⁺ ions, and electrons.

2. The Calvin Cycle (Light-Independent Reactions)

  • Location: Stroma (fluid surrounding the thylakoids)
  • Purpose: Fix carbon dioxide into organic molecules (glucose) using ATP and NADPH
  • Reactants: CO₂, ATP, NADPH
  • Products: Glucose (or G3P), ADP + Pi, NADP⁺

Summary of Photosynthesis

Equation:

6CO2 + 6H2O → C6H12O6 + 6O2.

Energy Flow:

Light → ATP & NADPH → Glucose

C6H12O6 = Glucose

Key Structures in Photosynthesis

  1. Chloroplast
    • Thylakoid: Site of light-dependent reactions.
    • Grana: Stacks of thylakoids.
    • Stroma: Fluid where the Calvin cycle occurs.
  2. Pigments
    • Chlorophyll a: Main pigment that absorbs light energy.
    • Accessory pigments: Help capture additional wavelengths of light (e.g., chlorophyll b, carotenoids).

Study Guide: Cellular Respiration

Overview of Cellular Respiration

Cellular respiration is the process by which cells convert glucose into energy in the form of ATP. It involves three main stages:

  1. Glycolysis
  2. Krebs Cycle (Citric Acid Cycle)
  3. Electron Transport Chain (ETC)

1. Glycolysis

  • Location: Cytoplasm
  • Reactants: Glucose, 2 NAD⁺, 2 ATP
  • Products: 2 Pyruvate, 2 NADH, 4 ATP (net gain: 2 ATP)
  • Purpose: Breaks glucose into pyruvate, producing ATP and NADH.

Key Steps:

  1. Glucose is split into 2 molecules of pyruvate.
  2. NAD⁺ is reduced to NADH.
  3. ATP is produced through substrate-level phosphorylation.

2. Pyruvate Oxidation (Link Reaction)

  • Location: Mitochondrial matrix
  • Reactants: 2 Pyruvate, 2 NAD⁺,
  • Products: 2 Acetyl-CoA, 2 NADH, 2 CO₂
  • Purpose: Oxidizes acetyl-CoA, generating NADH, FADH2, and ATP.

Key Steps:

  1. Pyruvate is transported into the mitochondria.
  2. It is converted into acetyl-CoA, releasing CO₂.

3. Krebs Cycle (Citric Acid Cycle)

  • Location: Mitochondrial matrix
  • Reactants: 2 Acetyl-CoA, 6 NAD⁺, 2 FAD, 2 ADP
  • Products: 6 NADH, 2 FADH₂, 2 ATP, 4 CO₂
  • Purpose: Converts pyruvate into acetyl-CoA, producing NADH and CO₂.

Key Steps:

  1. Acetyl-CoA combines with oxaloacetate to form citrate.
  2. Citrate is oxidized, producing NADH, FADH₂, and ATP. CO₂ is released as a byproduct.

4. Electron Transport Chain (ETC)

  • Location: Inner mitochondrial membrane
  • Reactants: NADH, FADH₂, O₂, ADP + Pi
  • Products: ATP, H₂O, NAD⁺, FAD+
  • Purpose: Uses NADH and FADH2 to produce ATP

Key Steps:

  1. Electrons from NADH and FADH₂ are transferred through the protein complexes of the ETC.
  2. Energy released by electron movement pumps H⁺ ions into the intermembrane space, creating a proton gradient.
  3. ATP synthase uses the flow of H⁺ back into the matrix to power ATP synthesis.
  4. Oxygen acts as the final electron acceptor, forming water (H₂O).

Total ATP Per Glucose Molecule

  1. Glycolysis: 4 ATP
    1. Uses 2 at the start of Glycolysis
    2. Produces a profit of 2 ATP
  2. Kreb’s Cycle: 2 ATP
  3. Electron Transport Chain(ETC): 30-32
  4. Total ATP produced: 36-38

Key Concepts

  1. Aerobic vs. Anaerobic Respiration:
    • Aerobic respiration uses oxygen and produces more ATP.
    • Anaerobic respiration occurs in the absence of oxygen, producing lactic acid or ethanol and CO₂ (in yeast).
  2. Proton-Motive Force:
    The ETC generates an electrochemical gradient of H⁺ across the inner mitochondrial membrane, which drives ATP synthase
  3. Role of Oxygen:
    Oxygen is the final electron acceptor in the ETC, enabling the continuation of NAD⁺ and FAD regeneration.
  4. Equation of Cellular Respiration: C 6 H 12 O 6 + 6 O 2 --> 6CO2 + 6H2O + ATP
    • C 6 H 12 O 6 + 6 O 2 = GLUCOSE